Clinical examination of squint

Presenter : Dr. Reshma
Clinical Evaluation
of Squint

HISTORY TAKING
VISUAL ACUITY
REFRACTION
EVALUATION OF MOTOR STATUS
EVALUATION OF SENSORY STATUS
ANTERIOR AND POSTERIOR SEGMENTS

1.HISTORY TAKING
2.VISUAL ACUITY &REFRACTION
3.EVALUATION OF MOTOR STATUS
 Inspection of eyes and Head posture
 Motor cooperation of eye-
Extraocular movements in 9 gaze positions
 Ocular deviation –
 Cover, Uncover,Alternate Cover,Prism Bar Cover Tests
 Corneal reflection Tests-Hirschberg’s,Krimsky,Bruckner test
 Maddox rod , Maddox Wing, Double Maddox Rod
 Diagnostic Occlusion
 Diplopia Charting,HESS Screen Test
 Synaptophore ,Major Amblyoscope
 Head tilt test
 Convergence,AC/A ratio
 Forced Duction test, Forced Generation test

•EVALUATION OF SENSORY STATUS
 Suppression-
 Worth 4 Dot Test
 4prism Dioptre Base Out Test
 Bagolinis Filter test,Maddox Rod test,After Image test
 Binocular perimetry,Haploscopy
 Retinal Correspondance-
 Afterimage test
 Striated Glasses of Bagolini,Major Amblyoscope,
Projection devices
 Diplopia Test
 Foveo foveal test of Cuppers
 Stereopsis
 Titmus fly test
 Random Dot test, TNO test
 LANG stereotest 1 & 2 , LANG 2 Pencil Test
 Synaptophore

• Related to fatigue or illness?
• More obvious in distance or near fixation?
• H/O defective vision
• Ass w/ Nystagmus or Diplopia
In case of Diplopia
• uniocular/binocular
• Duration
• Type of diplopia- horizontal /cyclovertical
• Direction of gaze in which it occurs
• Whether more marked in distance or near vision

• In ACUTE CASES
Precipitating factors like trauma, convulsions ,febrile episode
before onset of squint.
H/O neurological symptoms like loss of consciousness, motor
weakness,slurring of speech,giddiness,hemiparesis,tremors
H/o of previous surgery for squint, occlusion therapy, atropine
penalization
h/o Fever (viral meningitis)
h/o Long standing early morning headache with nausea and
vomiting (raised ICT)
h/o Hearing loss, tinnitus, vertigo
Tingling and numbness (multiple sclerosis)

Birth and medical history
• Significant antenatal history
• Maternal infection, any drugs taken during pregnancy
• Any untoward event during delivery
• Length of labour , Birth trauma, forceps, birth asphyxia
• Gestational age
• Birth weight of the child
• Developmental milestones, both physical and mental
• Other associated neurological problems like cerebral palsy,
epilepsy, mental retardation,craniofacial anomalies, behavioural
anomalies, handedness

INFANTS AND PREVERBAL CHILDREN (Birth – 14 months)
1.FIXATION PREFERENTIAL TEST(CSM METHOD)
• Central , Steady and Maintained fixation?
• Central foveal fixation
• Steady no nystagmoid movement
• Maintained ability to maintain fixation when converted from
monocular to binocular viewing
• Does he follow target?
• Does he get upset when 1 eye is closed?
2. OPTOKINETIC NYSTAGMUS
• Nystagmus elicited by passing a succession of black and white stripes in
field of vision
• Uses the minimum separable as a measure of visual acuity

3.FORCED CHOICE PREFERENTIAL LOOKING TEST
• attention more attracted by patterned stimulus than homogenous
surface
4.VISUAL EVOKED POTENTIAL
• Light stimulus to retina (checkerboard/stripes/unpatterned flash)
• Recorded by surface electrodes on occiput
• Changes in cortical electrical pattern

• Toddlers (14 m to 2 and half years)
1. HUNDRED &THOUSAND SWEET TEST
2. CARDIFF ACUITY TEST
3. DOTT VISUAL ACUITY TEST
4. STYCAR BALLS

Preschoolers (2 and half to 5 years)
1. LEA Symbols
2. Allen Picture Card
3. Broken Wheel Test
4. Tumbling E Chart
5. Landolt C Chart
6. Sjogren Hand Test
7. HOTV test
8. Isolated hand figure test
9. Sheridan –Gardiner HOTV test
10. Pictorial vision charts
(crowded KAY picture)
11. Bork candy bead test

School going children (5 to 15 years)
1. Tumbling E Chart
2. Landolt C Chart
3. Sjogren hand chart
4. Snellen’s Chart
5. LogMAR chart

RECOGNITION
ACUITY
LEA Symbols
HOTV
Snellen Chart
DETECTION
ACUITY
Stycar Ball
Test
RESOLUTION
ACUITY
LEA Paddles

• Under full cycloplegia (paralysis of ciliary muscles)
esp in childrenneutralize effect of accommodation which masks ref error
• Adequate cycloplegia- 1% cyclopentolate in 60 min
• In darkly pigminted irides or high hypermetropia –Atropine may be required
• <12 m 0.5% atropine
>12 m1% atropine
• Ass with hypermetropia(commonest), astigmatism ,anisometropia, myopia

HYPERMETROPIA
In a child with esotropia,esophoria
• Full cycloplegic correction even <2 years
In a child with exotropia .exophoria
• Under correction
ASTIGMATISM
>1.5 D  correction given especially after 18 months

MYOPIA
In a child with esotropia,esophoria
• Under correction
In a child with exotropia .exophoria
• Full cycloplegic correction

GOALS OF STRABISMUS EXAMINATION
1.Establishing a cause for strabismus
2. Diagnosing amblyopia
3.Measuring the deviation
4.Assessing binocular sensory status

HEAD POSTURE
• Face turn to right /left horizontal deviation
• Head tilt to right or left shoulder torsional deviation
Chin elevation or depression  vertical deviation
• To compensate for deviation
• To permit BSV
• To eliminate diplopia and place eyes in most comfortable position
• Patient position head to reduce need for affected muscle to contract

• Head placed in field of action of involved muscle ;eye moves out of field
of action
• In some , head placed in opposite field to increase separation between
diplopic images
• Head tilt to counteract torsional and vertical diplopia
• Chin elevation for weakness of vertically acting muscles
SO palsy Ocular torticollis
IN RSO,
• Chin depression
• Face turn to left
• Head tilt to left shoulder

• rule out pseudoptosis -on fixating with affected lid, lids will open
to normal width
• rule out jaw winking Marcus Gunn Phenomenon –whether lid
fissure width changes when jaw is moved or patient chews or
speaks
• rule out retraction syndrome - lid fissure changes when patient
moves eyes to left or right
• rule out pseudostrabismus-epicanthus (semilunar fold of skin
running downwards at side of nose with concavity directed
towards inner canthus)

PSEUDOTRABISMUS
• False appearance of squint in the absence of any deviation
• Even when visual axes are parallel, eyes seem to have a squint

VISUAL AXIS (line of sight)
• Line passing from fovea to point of fixation
PUPILLARY AXIS
• Line passing through centre of apparent pupil perpendicular to cornea and
meets retina on nasal side of fovea
ANGLE KAPPA
• Formed at the intersection of these 2 axes at centre of pupil

• When 1 eye is pointing in (towards the nose)Positive Angle Kappa
• When an eye is pointing out(away from the nose ) Negative Angle Kappa
• Normal fovea lies just temporal to anatomical axis
• light shown in centre of cornea cause reflex on visual axis just nasal to centre
of cornea (+angle kappa =5 degrees)

• Large +angle Kappa (in hypermetropia) pseudoexotropia
• Large - angle Kappa (in myopia)  pseudoesotropia

INTERPUPILLARY DISTANCE
Note ocular deviation by measuring Interpupillary Distance
1.Ordinary mm scale
2.Pulzone –Hardy rule
3.Synaptophore

TYPES OF EYE MOVEMENTS
1. Uniocular Eye Movements
Ductions
2.Binocular Eye Movements
Version : (Binocular Conjugate Eye Movements)
Vergence : (Binocular Disjugate eye movements)

Uniocular movements
Ductions – only one eye is open, the other covered/closed
tested by asking the patient to follow a target in each direction
of gaze.
Types of ductions:-

BINOCULAR MOVEMENTS
Versions:-
Binocular ,simultaneous, conjugate movements in same direction.
both eyes open, attempting to fixate a target &moving in same
direction.
Abduction of one eye accompanied by adduction of other eye is
called conjugate movements.

Types of versions:-
Dextroversion & laevo version
Elevation & depression
Dextro elevation & dextro depression
Laevo elevation & laevo depression

Vergences:
• binocular,simultaneous,disjugate/disjunctive movements
(opp.direction)
Convergence– simultaneous adduction
Divergence– outward movement from convergent position

• Abduction is normal when Temporal limbus touches lateral canthus
• Adduction is normal when Nasal 1/3rd cornea crosses nasal punctum
• Inferior ObliquesOn Lateral version, Upwards deviation from horizontal
line passing through centre of pupil
• Superior ObliquesOn Lateral version, Downwards deviation from
horizontal line passing through centre of pupil
• Abduction /adduction/infraduction should have at least 10mm of rotation
• Supraduction of 5-7mm

In paresis
• normal ductions observed due to extra innervation called in to
compensate for the paresis
• In versions this is picked up as extra innervation going to yoke
muscle which overacts
1.Primary underaction of involved muscle
2. Sec contracture of unopposed I/L antagonist
3.Sec contracture of yoke muscle
4. sec inhibitional palsy of C/L antagonist

• Hering’s law of motor correspondence states that when eyes
move into a gaze direction, simultaneous innervation leads to
yoke muscles having equal force
• Sherrington ‘s law of reciprocal innervation states that increased
innervation and contraction force of a given EOM is accompanied
by reciprocal decrease in innervation and contraction force against
its antagonist

In RSO palsy
1. If patient is looking up and left(in direction of I/L antagonist-RIO)
RIO receives reduced innervation  as it does not have to overcome the
normal antagonistic action of RSO (SH LAW)
But less innervation to C/l yoke of RIOLSR, giving false impression that LSR is
paretic(HER LAW)
Inhibitional palsy of contralateral antagonist
2. if looking down and right …more innervation required to move right eye to
abduction, C/L Yoke more innervated
 over acting LIR

HIRSCHBERG TEST
• Initial screening for strabismus
• Uses 1st purkinje image
• Gives rough estimate of angle of a manifest squint
• Useful in young uncooperative patients
• When fixation in deviating eye is poor
Procedure
1.Patient asked to fixate at point light 33cm away
2. Deviation of corneal light reflex from centre of pupil noted
Each mm deviation = 7 degree (1 degree =2 prism diopter approx)

KRIMSKY TEST
• Based on Herring Law of equal innervation
• for quick evaluation of angle of strabismus
• Used to centralize corneal reflection in
squinting eye as compared to reflex in fixing eye
• Results expressed in Prism Dioptres
PROCEDURE:
1.Patient asked to fixate on a point light
2. Prisms of increasing power (with apex towards direction of
manifest squint ) placed in front of Non Fixating eye till corneal light
reflex centred in squinting eye
3. Power of the prism required to centre light reflex = amount of
squint in PD

BRUCKNER TEST
• Performed using direct ophthalmoscope
• To obtain red reflex simultaneously in both eyes
• Deviated eye has a brighter and lighter reflex than fixing eye
• Helps in diagnosing media opacities, strabismus, refractive errors

PREREQUISITES FOR COVER
UNCOVER TEST
1. Ability to fixate target
2. Have central fixation in BE
3. No gross /severe mobility
defects
4. Vision >6/60 in both eyes
Simplest method to Distinguish
between phoria and tropia

COVER TEST
• Detects and confirms tropia (manifest)
Procedure:
1.Patient asked to fixate on a point light
2. Normal looking/fixating eye covered with occluder
3. Look for movement of uncovered eye
4. Test to be performed for near (33cm ) and distance (6m)fixation
5. To be done in all gaze fixations

• Covering one eye of patient with normal BSV interrupts fusion
• In presence of squint , uncovered eye moves in opposite direction
to take fixation
• In Apparent squint , no movement
• When eye is uncovered It will establish fixation

COVER UNCOVER TEST
• Detects and confirms phoria(latent)
• Observe covered eye as cover is removed
• In heterophoria covered eye will deviate towards heterophoric position
• Eg eye will move outward in presence of esophoria

ALTERNATE COVER TEST
• Identify TOTAL squint (tropia +phoria)
• More dissociative than cover uncover test
Procedure :
1.Hold occluder over 1 eye for several seconds
(which dissociates BSV)
2.Rapidly move occluder to other eye
3.Observe refixation shift of unoccluded eye, speed and
smoothness of recovery
4. Occluder is shifted back and forth several times
• Both eyes are covered alternatively
• Movement of covered eye noted as cover is changed from 1 eye to other

PRISM COVER TEST
• Single prism /prism bar used
• Measures amount of deviation in near or distance fixation in all gaze
positions in prism diopters
• Measures both heteroptropia and heterophoria
• Combines alternate cover tests with prisms
PROCEDURE:
1.Prisms of increasing strength with apex towards deviation placed in front
of 1 eye
BASE OUT –EsO
BASE IN ----ExO
2. Patient asked to fixate with other eye
3.Cover –Uncover test performed till
there is no recovery movement of eye
under cover

MADDOX WING
• Based on principle of dissociation by dissimilar objects
• Measures heterophoria for near (33 cm) in PD
• Through 2 slits,
RE sees vertical white arrow and horizontal red arrow
LE sees vertical and horizontal line of numbers

PROCEDURE:
1. patient asked to tell
• number on horizontal line which vertical arrow points (gives
amount of Horizontal phoria)
• Number on vertical line at which red arrow is pointing (vertical
phoria measurement)
2.Cyclophoria measures by asking patient to align red arrow with
horizontal line

MADDOX ROD
• Consists of multiple cylindrical high
plus lenses of red colour set together
in a metallic disc which converts
appearance of white spot of light into
a red streak
• Measures horizontal and vertical
deviations
• Dissociative –blocks fusion (measures
phoria)

PROCEDURE:
1.Patient asked to fix on a point of light in centre of
Maddox tangent scale at distance of 6m
2.Maddox rod is placed in front of 1 eye
• Maddox rod converts point light image into a line
• Thus patient sees a point light with 1 eye and a red
line with other
• Due to dissimilar images of 2 eyes, fusion is broken
and heterophoria becomes manifest
• The no: on Maddox tangent scale where red line
falls will be amount of heterophoria in degrees
• Dissociation b/w point light and redline can be
measured by superimposition of 2 images by prisms
in front of 1 eye with apex towards phoria

DOUBLE MADDOX ROD TEST
• Measures Tortional deviations
• Used in cyclodeviations
PROCEDURE:
• Maddox rod is placed in front of each eye (one red,
one white).
• Vertically aligned cylinders produce 2 horizontal lines
• Patient asked whether the 2 lines align exactly with
each other
• The colour of the tilted line is identified by the
patient.
• The corresponding Maddox rod is rotated until the
patient reports that it is vertical.
• The rotation required indicates the size of torsion.
• The two lines will fuse if there is no residual non-
torsional deviation.

SYNAPTOPHORE
• Measures angle of deviation
• Assesses retinal correspondance
• Checks for and measures fusion
• Assesses and measures Stereopsis
• Measures ocular alignment subjectively or
with cover testing
• When dissimilar targets are presented to each
eye,patient is asked to superimpose them
• If patient has NRC, horizontal, vertical, and
torsional deviations can be read directly fom
the calibrated scale.

PARK ‘S 3 STEP TEST
IN SO PALSY (4TH NERVE)

• Determine which eye is hypertropic
• 4 possible underacting muscles isolated
• Eg, IN STEP 1 if Right hypertropic means either
• 1. RE Depressors(RSO, RIR) are weak or
• 2. LE Elevators (LIO ,LIR)

• In STEP 2 , determine if vertical deviation greater in Ror L gaze
• Eg if its more in Left gaze, draw an oval around the 4 vertically
acting muscles used in left gaze
• Thus it might be either RSO or LSR

• STEP 3 involves tilting head to right and then to left
• Head tilt to right stimulates R intorters(RSR, RSO)
L extorters (LIR,LIO) and vice versa
If Vertical deviation increases to Right tilt implicates 4 muscles that act
vertically in right tilt around which oval is drawn
RIGHT SUP OBLIQUE is the only muscle with 3 circles
Around it

DIPLOPIA CHARTING
• Patient asked to wear Red and green diplopia charting glasses
• Red glass in front of right eye and green in front of left
• In a semi dark room, he is shown a linear light from a
distance of 4 feet and asked to comment on the images in
primary position and in other positions of gaze
• Patient tells about the position , Brightness and separation
of the 2 images in different fields

• Maximum separation in the field of action of paralytic muscle
• If 2 images are joined together No diplopia
• If images are separatedconfirms diplopia
• Maximum separation in the quadrant in which muscle is
restricted
• Image is displaced towards field of action of paralysed muscle
• HOR separation with uncrossed images Esodeviation
• HOR separation with crossed images Exodeviation
• VERT separation with uncrossed images Obliques involved
• VERT separation with crossed imagesVertical recti

HESS SCREEN TEST
Principles
1. Dissociation of eyes by Red and green goggles
2. Foveal projection in the presence of normal retinal correspondence
• Hering ‘s and Sherrington’s Law explain the development of muscle
sequelae
Uses
1. Diagnosis of underaction /overaction
2. Mechanical or neurogenic palsy
3.Planning of surgery & post op effects of surgery
4.Monitoring of condition

• Electronic Hess screen contains a tangent pattern
(2D projection of a spherical surface )printed onto
a dark grey background
• Red lights that can be individually illuminated by a
control panel indicate cardinal positions of gaze
within a central field (15 degree from primary
position) and a peripheral field (30 degree of
ocular rotation)
• Inner square of 8 dots and outer square of 16 dots

PROCEDURE:
1.Patient is seated 50 cm from the screen and wears red
Green goggle(red in front of right eye) & has a green pointer
2. The examiner illuminates each point which is used as point
of fixation
3.This can be seen only with RE ,which becomes fixating eye
4.Patient is asked to superimpose their green light on red
light, so plotting the relative position of the left eye
5. All points are plotted in turn
In Orthophoria, 2 lights should be more or less
superimposed in all 9 positions of gaze
6.Goggles are then reversed (red filter in front of left eye) and
procedure is repeated
7.The relative positions are marked by the examiner on Hess
chart and connected with a straight line

LEES SCREEN
• Is a modification of HESS screen
• Uses different method of dissociation
• Red and green complementary colour disso
ciation is replaced with double sided mirror
• Mirror prevents both eyes viewing same scr
een simultaneously although patient percei
ves both images seen by fovea of each eye
as if they are projected straight ahead

INTERPRETATION:
1.2 charts are compared
2. Smaller chart  eye with paretic muscle(RE)
3. Larger chart eye with overacting yoke
muscle (LE)
4.Smaller chart will show it greatest restriction in
main direction of action of paretic muscle (R LR)
5.Larger chart will show its greatest expansion In
main direction of action of yoke muscel (L MR)
6. Degree of disparity b/w plotted point and
template in any position of gaze gives an
estimate of angle of deviation

Forced duction test (FDT) (traction test)
• Simple and most useful method for diagnosing presence of mechanical
restriction of ocular motility
• To assess passive movement of the globe
• To differentiate b/w incomitant squint due to EOM paralysis and that due
to mechanical restriction of ocular movements
FDT +ve (resistance encountered during passive rotation) incomitant squint
due to mechanical restriction
FDT –ve  EOM palsy

PROCEDURE
1.4% LIDOCAINE
2.Supine position
3.Lids retracted
4. Patient asked to look in the direction of muscle being tested-
the paretic muscle (to relax antagonist )
If RLR possible paretic muscle ,patient asked to look to right
5.Eye held with toothed forceps applied to conjunctiva near the
limbus near insertion of possible mechanically restricted muscle
(on opp side of possibly paretic muscle )
Eg-If LR paresis, apply forceps near MR insertion
6.Eye is moved in the direction of action of muscle ( opp to that in
which mechanical restriction is suspected)
Eg-if LR was possible paretic muscle, eye grasped at medial limbus
and an abduction rotation movement attempted
If eye can be rotated with forceps past voluntary moved limit
presence of paretic muscle
If moves freely  Negative
RestrictedPositive

To distinguish b/w lateral rectus paralysis & mechanical
restriction involving the medial aspect of the globe, apply the
forceps at 6 and 12 o clock position and move the eye passively
into abduction
• NO RESISTANCE paralysis of lateral rectus muscle
• RESISTANCE mechanical restrictions do exist medially and
contracture of MR ,conjunctica ,tenon’s or MR myositis to be
considered

Forced generation test (FGT)
• Performed to differentiate b/w palsy vs Paresis in restrictive pathology
• To calculate potential force in apparently paralysed muscle
• To assess active muscle force which enables eye movement to take place
• Patient is asked to move in a given direction while the observer grasps
eye with an instrument
• If the muscle is paretic, examiner feels less than normal tension

DIAGNOSTIC OCCLUSION
• Used to induce full dissociation when its thought that maximum
angle of deviation has not been revealed
• Used in
Intermittent exotropia
To diagnose whether symptoms are due to heterophoria
To differentiate b/w real or apparent limitation of abduction in
children

CONVERGENCE
1. Place fixation object at 40 cm in midsagittal plane of patient ‘s head
2. Move the object towards the patient till 1 eye loses fixation and turns
out
This point is Near point of convergence (Normal 8-10 cm or less)
Dominant eye eye that maintains fixation

ACCOMMODATIVE CONVERGENCE/ ACCOMODATION RATIO
Amount of convergence (in Prism Dioptres)per unit change in Accomodation(in
Dioptres)
GRADIENT METHOD
• Dividing change in deviation (in PD)by change in lens power
• An accommodative target must be used and working distance held constant
(33cm or 6m)
• Plus or minus lens used to vary accommodative requirement
HETEROPHORIA METHOD
• Distance and near deviations and IPD used
If more exotropic or less eso at near fixation less convergence or low AC/A ratio
If more esotropic or less exo at near fixation high AC/A
In Accomodative eso a diff in eso of 10 PD or more b/w near and distance
fixation high AC/A

•EVALUATION OF SENSORY STATUS
 Suppression-
 Worth 4 Dot Test
 4prism Dioptre Base Out Test
 Bagolinis Filter test,Maddox Rod test,After Image test
 Binocular perimetry
 Stereopsis
 Titmus fly test
 Random Dot test, TNO test
 LANG stereotest 1 & 2 , LANG 2 Pencil Test
 Synaptophore
 Retinal Correspondance-
 Afterimage test
 Striated Glasses of Bagolini
 Major Amblyoscope
 Diplopia Test
 Foveo foveal test of Cuppers

WORTH 4 DOT TEST
• Dissociation test which can be used for both distance and
near fixation
• Differentiates b/w BSV, ARC, Suppression
PROCEDURE:
1.Patient wears red green goggles with red lens in front of
right eye
2.Patient is seated in a dark room
3.He views an illuminated box with 4 circular lights-
2 green lights
1 red light
1 white light
4. Testing distance can be varied to identify size of
suppression scotoma
5.Red light seen through red filter;Green through green
filter;white light by both eyes
White light is only binocular fusion target

• 4 dots Normal Retinal Correspondance
In ARC, with Manifest Squint
• 5 dotsEsODEVIATION-Uncrossed (red on right)
• ExODEVIATION-Crossed (red on left)
• 3 green dotsSuppression of Right eye
• 2 red dots Suppression of left eye

4 D PRISM TEST
• Main aim- to prove the presence of normal BSV
• Test done to detect a small central suppression scotoma (or foveal
suppression).
• In patients who have decreased stereopsis but are orthophoric on cover
testing.
• In small to intermediate angle deviations
• The level of dissociation is mild

Procedure
1. Instruct the patient to look at a distance target.
2. A 4-BO prism is quickly placed over RE with base out and the examiner
observes the movement of LE.
3. A sudden displacement of the image onto the parafovea will cause re-
fixation if the image is falling on corresponding points on a normal
retina.
4. The test is repeated on LE and the examiner observes the movement
of the RE.
• Strength of prism moves image a little bit in foveal arealeading to
recovery movement in other eye
• no movement will occur if the image has been shifted within a
nonfunctioning (scotomatous) area

Interpretations
• When the test is negative, the patient is
considered to be bifoveal.
When the prism is over the right eye, the
left eye moves out and in.
When the prism is over the left eye the
right eye goes out and in.
• There are two responses when there is a
scotoma (microtropia).
There is a scotoma on the right eye if the
prism is over the right eye and there is no
response bilaterally
vice versa for the fellow eye

BAGOLINI STRIATED GLASSES
• It detects BSV or suppression
• Evaluation of near and distance retinal corrrespondance
with minimal dissociations
• Each lens of Bagolini Glasses have fine parallel striations
which convert point source of light into a line
PROCEDURE:
1.2 lenses placed at 45 and 135 degrees in front of each
eye respectively
2. Patient asked to fixate a small light source
Testing distance at 6m and 33 cm
3.Each eye perceives an oblique line of light perpendicular
to that perceived by fellow eye
4. Can be used in any desired gaze

RESULTS:
• 2 streaks intersect at their centres in form of
oblique cross  BSV or ARC of harmonious type
• 2 lines but not forming crossIncomitant squint
with NRC
• Only 1 streak no simultaneous perception and
suppression of other eye
• Small gap in one of the streakCentral
suppression Scotoma

TEST FOR FIXATION
Visuoscope or Fixation Star of Ophthalmoscope
• Patient asked to cover 1 eye and fix the star with other eye
• Fixation may be
• CENTRIC
normal on the fovea
• ECCENTRIC
unsteady
Parafoveal
Macular
Paramacular
peripheral

SYNAPTOPHORE
• Consists of 2 tubes, having a right angled bend, mounted
on a base
• Each tube has a light source for illumination and a slide
carrier at outer end and a reflecting mirror at right angled
bend and eyepiece of +6.5 D at inner end
USES
• to diagnose anomalies of binocular vision with targets that
are presented to each eye
• To assess deviation and quantify binocular vision(Precise
measurement of angle alpha, Objective and subjective
angle of deviation, Vertical and tortional deviations)
• To detect and quantify area and density of suppression
• To detect ARC
• To measure fusional amplitudes,Stereopsis

PROCEDURE:
1. The patient is instructed to place chin on the chin rest.
2. Chin rest and IPD adjusted accordingly.
3. The examiner uses the toggle switches to show the patient the slide
illuminated to right and left eye.
4. As the examiner switches the toggle from the right eye to the left eye it is
representative of cover testing.
5. The eye that is illuminated is the eye that is fixating.
6. The examiner should be able to see the eye movements and be able to
neutralize a horizontal deviation by using the arms at the side of the
machine.

• There is a scale near the arms to note the size of deviation.
Neutralizing a vertical deviation requires the use of the R/L Hyper
knobs.
Cyclo deviations are also neutralized using the appropriate knobs
Near deviations can be neutralized by placing a -3.00 sphere trial
lenses in the lens holder in front of the eyepiece. This way, the
patient has to exert 3 D of accommodation to make the objects
clear.

• The goal of the examiner is to have the patient fuse the fusion
targets
• Worth’s Grade 1 slides( red slides) simultaneous perception
slides -test subjective and motor angles.
• Grade 2 slides (green) -test motor and sensory fusion.
• Grade 3 slides (yellow) stereoscopic vision slides and -test the
presence of third grade binocularity

• Examination of simultaneous perception  determination of
angle of strabismus and retinal correspondence assessment
• Fusion amplitude evaluated with use of nearly same pictures,
differing in only small details
• Stereoscopy examined with use of slightly decentred special
pictures, which are projected on disport retinal point, within
Pannum ‘s area, giving the impression of depth and stereoscopy

Measurement of Angle of Anomaly:
• denotes the degree of shift in visual direction.
• determined by calculating the difference between the objective and
subjective angles of deviation.
Procedure :
1.The arms of the synaptophore are set at zero.
2. Both the arms of the instrument are moved by the examiner while
alternately flashing the light behind each slide until there is no further
fixation movement of the patient’s eye (alternate cover test).
3.The reading of both the arms is noted at this moment and the sum total of
the reading of both the arms gives the objective angle of anomaly(MOTOR
ANGLE )
4.The subjective angle of anomaly (SENSORY ANGLE )is the angle at which
the visual targets are superimposed, there is no shift and the deviation is
neutralized .
Angle of Anomaly = Objective Angle – Subjective Angle

The interpretation of this test is as follows-
•If Subjective Angle = Objective Angle → NRC
•If Subjective Angle < Objective Angle → ARC
•If Angle of Anomaly = Objective Angle →Harmonious ARC
(full sensory adaptation)
•If Angle of Anomaly < Objective Angle →Unharmonious ARC

AFTER IMAGE TEST
• In patients who can fixate with foveal area
• To determine ARC and dense suppression
• Highly dissociating orthoptic test
PROCEDURE:
1.In dark room occlude non dominant eye
2. Dominant eye to be stimulated in direction of strabismus
Horizontal beam for horizontal strabismus and vertical beam for vertical
strabismus
3. Non dominant eye getting opposite beam
4. Patient fixates on lighted beam for 10 sec so that fovea is stimulated
5.Patient instructed to close eyes and observe white lines(POSITIVE
AFTER IMAGE) asked to draw position
6.After lights on patient instructed to see blank wall to see black line
(NEGATIVE AFTER IMAGE)

If Retinal correspondence is Normal draws a cross
In case of suppression draws 1 line
Esotropic with ARC draws vertical image to left of horizontal
Exotropic with ARC draws vertical image to right of horizontal

FOVEO FOVEAL TEST OF CUPPERS
• In patients with eccentric fixation
• An asterisk placed on fovea of deviated eye (under visuoscopic guidance)
• Other eye fixates the light on a Maddox cross or tangent screen
• If one breaks through suppression scotoma of deviated eye, patient can
report position of images
• In NRC Fixation target superimposed on central fixation light of Maddox
crossfovea have common visual direction
• In ARCThe asterisk superimposed on one of the numbers on the
horizontal bar of Maddox scale, number indicating angle of anomaly in
degrees

FIELD OF BINOCULAR VISION
• Tested in patients with paralytic squint with some field of single
vision
• Performed on the perimeter using a central chin rest

NEUTRAL DENSITY FILTER TEST
• Visual Acuity is measured without and with neutral density filter
placed in front of the eye
• In functional Amblyopia Visual Acuity slightly improves
• In organic amblyopia VA markedly reduced when seen through
the filter

TESTS FOR STEREOPSIS
Based on 2 principles
1.Using targets in 2 planes ,constructed so that they stimulate
disparate retinal elements , giving a 3D effect
Eg- Concentric rings, Titmus fly test, TNO test, Random Dot
Stereograms, Polaroid Test, Langs stereo test, Stereoscopic targets
presented haploscopically in Major Amblyposcope
2.Using 3 D targets
Eg-Lang ‘s 2 pencil test

QUALITATIVE TESTS FOR STEREOPSIS
1. Lang’s 2 pencil test
2. Synaptophore
QUANTITATIVE TESTS FOR STEREOPSIS
1. Random Dot test
2. TNO test
3. Lang’s stereo test
METHODS USING POLARIZATION
Targets provided as vectographs and images seen by 1 eye is polarized at
90 degree using polarized glasses
1. Titmus Fly test
2. Polaroid test
3. Random dot stereograms
4. TNO test

VECTOGRAPHS
• Consists of polaroid material on which 2 targets imprinted so that
they are polarized at 90 degrees with respect to each other
• Patient provided with Polaroid Spectacles so that each target is
seen separately with 2 eyes
• TITMUS STEREO TESTS:
3D polaroid vectograph made of 2 plates in form of a booklet
• 3 PARTS-1.FLY TEST
2.ANIMAL TEST
3.CIRCLE TEST

1.FLY TEST
• Right side of booklet – large housefly
• To test gross stereopsis
• Threshold 3000 sec of arc
• Useful in young children
• If subject asked to pick up one of the wings of fly and
subject sees stereoscopically he will reach above the
plate
• In absence of gross stereopsis fly appears as flat
photograph

2.ANIMAL TEST
• If gross stereopsis present
• Test consists of 3 rows of 5 animals each,1 animal from each row
imaged disparately (threshold 10,200, 400 sec of arc respectively)
• In each row , 1 of the animals correspondingly imaged in 2 eyes printed
heavily black (misleading clue)
• Subject asked which animal stands out
 subject with stereopsis will name the disparately imaged animal
 subject without stereopsis will name the animal printed black

3.CIRCLE TEST
• Consists of 9 squares, each containing 4circles arranged
in form of lozenge
• Only 1 circle in each square is disparately images at
random threshold (800 to 40 sec of arc)
• If subject has passed other 2 tests , he is asked to PUSH
DOWN the circle that stands out
• When he finds no circle to push or makes a mistake
limit of his stereopsis presumably reached
• Circle no 5 equivalent to 1 sec of arclowest limit of
fine central stereoacuity

RANDOM DOT STEREOGRAM TEST
• Devoid of monocular clues
• Patients cannot guess what stereo figure is and where it is located
• Provides truer measurement of stereopsis than Titmus test

TNO TEST
• Each test plate consists of a stereogram in which images presented to
each eye have been superimposed and printed in complimentary colours
• Stereograms are viewed through a pair of red and green filters
• Random dot Stereograms have the advantage that they completely
eliminate monocular cues, the patient is required to describe the shape
which can be only seen stereoscopically

• TNO Test has 7 plates
• 1st 4 plates are for screening purposes,the disparities are large and ungraded
PLATE I  2 Butterflies of which 1can be seen monocularly, other
only in stereopsis
PLATE II  4 discs, 2 seen monocularly , 2 need stereopsis
PLATE III  4 hidden shapes arranged around centrally placed cross
PLATEIV Suppression test.There are 3 discs,1 seen by right eye,1
by left , 1 seen binocularly
PLATE V-VII test shapes (PAC man Shapes )presented at 6 different
disparities ranging from 15-480 secs of arc

LANG ‘S STEREO TEST
• Cards are held at the subject’s reading distance and he or she is asked to
name or point to the pictures
• Displacement of random dots creates the disparity which ranges from 1200
to 550 secs of arc

FRISBY STEREO TEST
• Only clinical test based on actual depth , where random
shapes are printed on 3 clear plastic plates of different
thickness
• Doesn’t require any form of dissociation
• Each plate has 4 squares of curved random shapes
• 1 square contains a hidden circle that is printed on the
opposite surface
• Disparities range from 600 to 15 secs of arc
• Care taken that neither the plates nor the patient ‘s head
move during testing as this may provide monocular cues
• If the 1st plate is recognized successfully , then thinner
plates, which give smaller disparities, are presented in a
similar fashion

SIMPLE MOTOR TASK TEST
2 PENCIL TEST:
• Detect presence or absence of gross stereopsis (threshold
value 3000-5000 sec of arc)
PROCEDURE:
1. Examiner holds pencil vertically in front of the patient
2. Ask patient to touch its upper tip with the tip of the
pencil in his hand with 1 swift movement from above
3. Patient having stereopsis passes the test with both eyes
open

• Examination of
• Associated lid problems
• Ptosis
• Media opacities
• Examination of pupillary reflexes
• Underlying optic nerve or retinal
pathologies
• Examination of fundus in
• Excluding macular pathology
macular scarring
optic disc hypoplasia
retinoblastoma
• Objectively observing torsion of eye

REFERENCES
1. Binocular Vision and ocular motility by GUNTER K. VON NOORDEN
2. Pediatric ophthalmology and Strabismus AA0 section 06
3. Practical Orthoptics by T. Keith Lyle
4. Strabismus Simplified by Pradeep Sharma
5. Kanski Clinical Ophthalmology

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